Conventionally, there have been proposed a 360-degree toothbrush as described in Patent Document 1, as a kind of toothbrush. The toothbrush has a cylindrical brush head in a tip portion of a brush handle. The cylindrical brush head is constructed by laminating disk-shaped radial vanes in a central axis direction. A conventional structure of a disk type radial vane is shown in FIGS. 11(a) and 11(b).
A disk-shaped radial vane 1 is constructed by a disk-shaped annular core part 2 in which a tip portion of a brush handle passes through its inner side, and a radial vane part 3 which is formed by extending a lot of thread materials 21 to an outer peripheral direction from a whole region in a peripheral direction of the annular core part 2. The annular core part 2 is a weld part to which a lot of thread materials 21 are connected, and an inner side of the annular core part 2 forms a through hole 4 for inserting the handle. In the radial vane 1 described in Patent Document 1, in order to make density of flocked fabric in a central axis direction in the brush head small, annular protrusions 5 are integrally formed in both surfaces of the annular core part 2 so as to form a so-called boss part.
As a method of manufacturing the radial vane as mentioned above, there has conventionally employed methods which are basically based on the same principle, as described in Patent Documents 1 to 3. A manufacturing principle will be described with reference to FIG. 12. A manufacturing apparatus of the radial vane manufactures the radial vane 1 from a thread bundle 20 which is formed by bundling the thread materials 21 of nylon resin. For this manufacturing, the manufacturing apparatus is provided with a horizontal processing bed 30 and a columnar welding head 40 which is provided on the bed.
The processing bed 30 is provided with a vertical through hole 31 through which the thread bundle 20 passes. The columnar welding head 40 is arranged on the through hole 31 of the processing bed 30 so as to be concentrically vertical, and is driven up and down in the central axis direction by a driving mechanism (not shown). The welding head 40 is a welding horn which carries out welding on the basis of supersonic vibration, and is oscillated and driven by a vibrator (not shown). A circular tip face of the welding head 40 is a weld surface 41.
In the manufacturing of the radial vane 1, first of all, the thread bundle 20 protrudes at a predetermined amount onto the processing bed 30 through the through hole 31 of the processing bed 30 in a state in which the welding head 40 on the processing bed 30 is in an upward evacuated position. The thread bundle 20 is pushed up by a push-up chuck which is provided below the processing bed 30 and is not shown. A protruding amount of the thread bundle 20 is set according to a radius of the radial vane 1 to be manufactured/
In the case that the thread bundle 20 protrudes at the predetermined amount onto the processing bed 30, the welding head 40 moves down while vibrating from the upward evacuated position, and the thread materials 21 forming the protruding part are uniformly expanded to the periphery by the tip portion of the welding head 40. On the basis of the further continuous downward movement of the welding head 40, the periphery of the center part of the radially opened thread materials 21 is finally pressed to the periphery of the through hole 31 on the surface of the processing bed 30, by the weld surface 41 of the welding head 40. As a result, the thread materials 21 in the protruding part of the thread bundle 20 are bent vertically to the periphery and are open radially, and the periphery of the center part of the radially opened thread materials 21 is welded by the weld surface 41 in a tip of the welding head 40. Further, the center part of the radially opened thread materials 21 is promoted to be welded by heat transmission from the periphery of the center part, and finally forms a welded and solidified part 25.
In the case that the periphery of the center part of the radially opened thread materials 21 is welded, an annular weld part 22 thereof is separated from an inside thread bundle part. As a result, the completed radial vane 1 is separated from the thread bundle 20, and the annular weld part 22 forms the disk-shaped annular core part 2 in the radial vane 1. Further, the welded and solidified part 25 formed in the tip portion of the thread bundle 20 is cut and removed in preparation for manufacturing the next radial vane 1, after separating the completed radial vane 1.
In the manufacturing method described in Patent Document 1, the boss parts (the annular protrusions 5 and 5) for making the density of flocked fabric in the central axis direction in the brush head small are integrally formed by flowing of the melting material during welding in the periphery of the center part of the radially opened thread materials 21 (during formation of the annular weld part 22). Further, in the manufacturing method described in Patent Document 3, the periphery of the center part of the radially opened thread materials 21 and the center part are formed and separated by a cylindrical separation jig doubling as a guide of the thread bundle 20 during welding of the periphery of the center part of the radially opened thread materials 21, and it is possible to achieve reduction of a manufacturing man hour and shortening of a manufacturing time.
On the other hand, in the manufacturing method described in Patent Document 2, in order to enlarge density of the thread materials in the vane parts 3 of the completed radial vane 1 and in order to enhance mechanism strength of the annular core part 2, the thread bundle 20 is protruded onto the radial vane 1 again through the through hole 4 which is formed in the inner side of the annular core part 2, while keeping the completed radial vane 1 at a fixed position on the processing bed 30, the periphery of the center part is welded annularly by again opening the thread bundle 20 to the periphery, and the inner side of the annular weld part 22 is separated. According to the structure, the radial vane 1 of double structure (two-ply structure) integrated by the annular core part 2 is manufactured.
However, in any manufacturing method, whenever the radial vane 1 is manufactured on the processing bed 30, the tip portion of the thread bundle 20 separated from the radial vane 1 forms the welded and solidified part 25, and is cut and removed since the tip portion forms an obstacle at the manufacturing time of the next radial vane 1. A length of the removed part reaches about 3 mm to be on the safe side, and a cut loss of the thread bundle 20 generated thereby increases a manufacturing cost, and forms a great obstacle against reduction of the manufacturing cost. In the case of the radial vane 1 of double structure described in Patent Document 3, two removed parts are generated every time one radial vane 1 is manufactured. Therefore, the cut loss of one thread bundle 20 comes to several mm.
An inner diameter of the through hole 4 in the radial vane 1 basically coincides with an outer diameter of the thread bundle 20. The inner diameter of the through hole 4 can be made larger, however, it is necessary to more greatly remove the annular weld part 22 (the annular core part 2), and the cut loss caused by the weld part separation in the thread bundle 20 is further increased.
Further, the annular core part 2 of the manufactured radial vane 1 is thin and hard (due to no elasticity) since the thread materials 21 are formed by the supersonic welding. Therefore, in the case that the inner diameter of the core part (the diameter of the inside through hole) is smaller than the outer diameter of the shaft part of the handle, not only work becomes hard when the radial vane 1 is fitted to the shaft part, but also the annular core part 2 is easily broken. On the contrary, in the case that the inner diameter of the through hole 4 (the handle insertion hole) formed in the inner side of the annular core part 2 is large, the radial vane 1 is not fixed to the shaft part, and idle running at the using time comes to a problem.
As a result, since strict precision is demanded in the inner diameter of the annular core part 2, and the articles having defective precision are increased, the manufacturing cost of the radial vane 1 is increased.